The present invention generally relates to packaging and more particularly is directed to a rotating stretch wrapping apparatus and method for making unitary packages which hold a plurality of components, each package containing a load wrapped on all sides by a web of stretched film.
Case packing or boxing is a common way of shipping multiple unit products which need to be enclosed. Multiple unit products are generally stacked in a corrugated box or are wrapped with kraft paper with the ends of the kraft paper being glued or taped.
Some manufacturers use steel or plastic strapping to unitize the product. The problems incurred in the use of strapping are the requirement of costly corner protectors, danger of bending or snapping and possible injury to the operator while applying this high tension material to the loads. In addition there is the ever present problem of settling due to moisture wetting the cartons, and the sides of the cartons bulging or normal vibrations causing the straps to loosen and the load to come apart.
Glue is an alternative method for some packaging usages but customer dissatisfaction with gluing is high because removal of glued cartons or bags from the unitized loads tends to tear outside layers of the cartons. Glue, although an inexpensive material, demands interleaving for product orientation requiring more durable and expensive packaging material.
Because of the lack of alternatives of packaging, tape is currently being used to horizontally bind the top layer of the load. However, tape is expensive and allows relatively free movement of all product surrounded.
Another way of shipping products is by putting a sleeve or covering of heat shrinkable material around the products and shrinking the sleeve to form a unitized package. The use of heat shrinkable film is described in U.S. Pat. Nos. 3,793,798; 3,626,654; 3,590,549; and 3,514,920. A discussion of this art is set forth in U.S. Pat. No. 3,867,806.
The present invention is designed to function with stretchable film webs of plastic material such as nylon, polypropylene, PVC, polybutylene, polyethylene or any copolymer or blends of the aforementioned stretchable films.
An economical way of packaging products currently being used is by wrapping the product load with a web of stretched plastic film.
The elasticity of the stretched plastic film holds the product of the load under more tension than either shrink wrap or kraft wrap, particularly with products which settle when packaged. The effectiveness of stretched plastic film in holding a load together is a function of the containment or stretch force being placed on the load and the ultimate strength of the total layered film wrap. The strength is determined by the modulus or hardness of the film after stretch has occurred and the containment force is currently achieved by maximizing elongation until just below a critical point where breaking of the film occurs.
The use of wrapping machinery to wrap stretched film around a load is well known in the art. Four types of stretch wrapping apparatus are commonly used in the packaging industry and these types are generally described as spiral rotary machines, full web rotary machines, pass-through machines, and circular rotating machines.
A spiral machine is shown in U.S. Pat. No. 3,863,425 in which film is guided from a roll and wrapped around a cylindrical load in a spiral configuration. A carriage drives the film roll adjacent the surface of the load to deposit a spiral wrap around the load and returns in the opposite direction to deposit another spiral overwrap around the load.
In U.S. Pat. No. 3,788,199, tapes are spirally wound in such a manner that they overlap each other to provide suitable space therebetween when breatheability is required. In this disclosure, a heavy duty bag is prepared by spirally winding stretched tapes of synthetic resin in opposite directions, so that they intersect each other to form a plurality of superimposed cylindrical bodies which are bonded together to form a cylindrical network. The spirally wound inner and outer tapes of the superimposed cylindrical body intersect each other at a suitable angle, depending upon the application intended, the preferred embodiment having substantially equal longitudinal transfer strength. In the preferred embodiment, the tapes intersect each other at an angle of about 90 degrees. The angle defined by the tapes constituting the cylindrical network may be determined by varying the interrelationship between the travelling speed of the endless belts carrying the tape and the rotating speed of the bobbin holders, which rotates a plurality of tape bobbins to deposit the tape onto the moveable belt.
Spiral wrapping machines which are currently commercially available are manufactured by Lantech, Inc. under Model Numbers SVS-80, SVSM-80, STVS-80, STVSM-80 and SAHS-80.
A full web type of apparatus which wraps stretched film around a rotating load is disclosed in U.S. Pat. No. 3,867,806 assigned to Lantech, Inc. A similar full web apparatus using a tensioned cling film wrapped around a rotating load is shown by U.S. Pat. No. 3,986,611 while another apparatus using a tacky PVC film is disclosed in U.S. Pat. No. 3,795,086.
Full web wrapping machines typical of those presently commercially available are Model Numbers S-65, T-65, and SAH-70 manufactured by Lantech, Inc.
Another type of machine for wrapping a pallet load commonly called a pass-through machine is disclosed in U.S. Pat. No. 3,596,434. In this reference a pallet load is transported along a conveyor and the leading face of the pallet load contacts a vertical curtain of film formed by the sealed leading edges of film webs dispensed by two rolls of film on opposite sides of the path of the pallet load. The pallet load continues to move along the conveyor, carrying with it the sealed film curtain until the two side faces of the pallet load as well as the front face are covered by film web. A pair of clamping jaws then close behind the pallet load, bringing the two film web portions trailing from the side faces of the pallet load into contact with one another behind the pallet. The jaws then seal the film web portions together along two vertical lines, and cut the web portions between those two seals. Thus, the film web portions are connected to cover the trailing face of the pallet load, and the film curtain across the conveyor is re-established to receive the next pallet load. The pallet load may subsequently be exposed to heat in order to shrink the film web and apply unitizing tension to the load, as is disclosed in U.S. Pat. No. 3,662,512. Another disclosure of relevance to pass-through wrapping is U.S. Pat. No. 3,640,048 which shows that film may be applied to the top and bottom of the pallet load prior to the wrapping cycle when it is desired to cover all six surfaces of the pallet load with film. Commercial pass-through machines are currently manufactured by Weldotron, Arenco, and SAT of France.
Various apparatus and processes have been developed to rotatably wrap stacked components to form a load.
Stationary loads which are brought to a loading area and are wrapped by a rotating member which dispenses stretched film around a load are disclosed in U.S. Pat. Nos. 4,079,565 and 4,109,445. U.S. Pat. No. 4,079,565 discloses a full web vertical wrap of a load while U.S. Pat. No. 4,109,455 discloses a horizontal spiral wrap of a load.
U.S. Pat. No. 4,050,220 discloses a wrapping device for multiple unit loads. Each load is conveyed to a wrapping area in which a load is supported on one or more stationary planar surfaces. The leading edge of a roll of stretchable plastic wrapping material is held adjacent to the load, and the roll of material is rotated about the load and the supporting planar surfaces, wrapping the load and the supporting surfaces together. Plastic wrapping material is stretched during the wrapping operation so that the material is under tension when applied to the load. After the wrapping cycle is complete, the load is pushed past the ends of the supporting surfaces, and the wrapping material which covered the supporting surfaces collapses against the supported sides of the load. Further developments of this type of wrapping system are disclosed in U.S. Pat. Nos. 4,110,957 and 4,178,734.
U.S. Pat. No. 603,585 discloses a spiral wrapping device for enclosing individual newspapers in paper wrap for mailing purposes. Each newspaper is placed on a cylindrical core with a circumference approximately twice that of a newspaper, and each newspaper advances along the length of the core as the core is rotated. Wrapping paper is applied to the core at an angle and the wrapping paper trailing each newspaper is severed as each newspaper reaches the end of the cylinder and is placed on a flat horizontal surface, thereby collapsing the wrapping paper against the underside of the newspaper previously pressed to the cylinder.
U.S. Pat. No. 1,417,591 discloses a wrapping machine for individual items such as boxes in which each such item is conveyed along the surface of a horizontal sheet of wrapping material. The edges of wrapping material on each side of an item are curled upward to meet one another atop the item to be wrapped thereby forming a tube around the item. The leading end of the tube is sealed and the trailing end of the tube is severed and then sealed to enclose the item. Another device which utilizes this system of wrapping is disclosed in U.S. Pat. No. 3,473,288.
In U.S. Pat. No. 2,575,467, a wrapper of cylindrical packages for material such as sausage is disclosed in which the package is rotated about its cylindrical axis as wrapping tape is applied at an angle to form a cylindrical wrap.
In U.S. Pat. No. 2,863,270, two cylindrical items of approximately equal diameter are abutted at their planar ends, and placed by hand in a cradle which exposes the complete circumference of the abutting ends. A roll of wrapping material is then driven by a hand crank mechanism to circulate around the circumference of the abutting ends, applying wrapping material thereto. When sealed together, the pair of cylindrical items are removed from the cradle by hand.
A spiral wrapping machine for long bundles of items such as filaments is disclosed in U.S. Pat. No. 3,000,167. As the bundle of filaments moves along its axis through the wrapping area, a ring circulates about the bundle carrying a roll of wrapping material which is applied to the bundle to form a spiral wrap pattern. Because the normal load of filaments or similar items is much longer than the wrapping area, it is not necessary to provide support for the bundle in the wrapping area and therefore no support structure is wrapped with the bundle.
Commercial circular rotating wrapping machines are presently manufactured by Lantech, Inc. under the trademark LANRINGER and are provided with wrapping ring inner diameters of 36 inches, 54 inches, 72 inches and 84 inches. In differentiating between the various circular rotating wrapping machines manufactured by Lantech, Inc., the manual model has the designation SR; the full web models have the designations SVR and SAVR; the multiple banding models have the designation SVBR and SAVBR; the spiral models have the designation SVSR and SAVSR and the continuous wrap or bundle models have the model designations SVCR and SAVCR.
In these commercial machines, the load is pushed onto support tongues or wrapping rails and the load and support tongues are wrapped by a rotating supply of film. The film is stretched as it is rotated from the dispenser and the stretched film wrap holds the load together under compressive forces and also engages the tongues or wrapping rails on which the load is supported. The load is then pushed off or carried off on the tongues by the following load or take-off conveyor respectively with the attendant frictional forces which result from the film engaging the tongues. Alternately the load as it is fed into the rotating wrapping apparatus is carried through the wrapping station by a conveyor assembly having an upper conveyor which carries the load in a downstream direction and a lower conveyor mounted under the load carrying conveyor. The lower portion of the endless belt of the lower conveyor travels at the same speed and in the same direction as the upper portion of the endless belt of the load carrying conveyor so that stretched film wrapped around the load and conveyor assembly is carried by the lower conveyor at the same speed and in the same direction as the load is carried by the upper conveyor. The wrapped load is transported to a take-off conveyor spaced from the conveyor assembly allowing the wrap to be transported off of the conveyor assembly to assume a memory position around the load before it is carried off by the take-off conveyor.
In the previously described circular bundling machines, the loads are wrapped with stretched film web and severed, leaving a package which is open ended at its leading and its trailing ends, thus, exposing the package to elements, spillage, damage and theft. While this problem can be overcome with the use of a wrapping machine downstream from the continuously wrapped loads which wraps the ends with another wrap, it can be seen that such a process is time-consuming and expensive, both from a materials usage and from a labor standpoint. This problem has been solved in several applications but unfortunately, these applications are not applicable to wrapping commercial loads in a manner shown in the present invention. One manner of solving this problem is through the use of a continuous tubing which is then stuffed with material. The tubing is then compressed at various intervals and the compressed portion of the tubing is sealed together by a heat seal mechanism as shown in U.S. Pat. No. 3,001,384 or tied together with a hog-ringer. In another embodiment, two overlapping layers of material are heat sealed around the package at their outer perimeter. Such a method of wrapping an article in plastic film is shown in U.S. Pat. No. 3,381,444.
One solution for large commercial load wrapping is shown in U.S. Pat. No. 3,902,303 in which a bag is placed over a commercial pallet load and then heat shrunk around the load to make the unitary package.
However, the prior art exhibits a widespread deficiency: a continuous wrap of stretch film web cannot be extended effectively between consecutive loads of varying circumferences. The maintenance of film web under tension between loads is especially desired so that severence of consecutive loads causes the severed film to collapse against load ends and provide containment force. For loads of circumferences greater than the width of the film web, a film tube short enough to be supported by consecutive loads alone, i.e. of length less than the film web width, cannot provide sufficient collapsed film when severed to cover both load ends. Further, and regardless of the width of the film or the length of the tube, when a film tube extends from a load of smaller circumference to a load of larger circumference, severence necessarily results in slack at the smaller load and inadequate coverage at the larger. It is the object of the present invention to provide an apparatus which spirally wraps consecutive loads carried by a conveyor, thereby forming a film tube between consecutive loads which is maintained under tension regardless of the relative sizes of consecutive loads. Thus, the present invention permits wrapping of consecutive customized items such as, for instance, rugs, of widely varying circumferences with subsequent severence causing collapse of film web against load ends to provide containment force and protection from exterior elements.